#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
#define rep(i, a, b) for (int i = (a); i <= (b); i++)
#define per(i, a, b) for (int i = (a); i >= (b); i--)
#define endl '\n'
const int N = 105;

int n, m;
int a[N];
int p[65];
bool add(int x) {
  per(i, 29, 0) {
    if (x >> i & 1) {
      if (!p[i]) {
        p[i] = x;
        return true;
      } else {
        x ^= p[i];
      }
    }
  }
  return false;
}
int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  cin >> n;
  rep(i, 1, n) cin >> a[i];
  sort(a + 1, a + n + 1);
  ll ans = 0, cnt = 0;
  per(i, n, 1) {
    if (!add(a[i]))
      ans += a[i];
    else
      cnt++;
  }
  if (!cnt)
    cout << -1;
  else
    cout << ans;
  return 0;
}